Development of an individual is in a large part governed by genes, but the effects of the environment should not be discounted. Our five-year project sponsored by the Grant Agency of the Czech Republic is focused on the role of epigenetic influences (temperature, drugs, experimental hemodynamic perturbations) on cardiac development. We use the chick embryo model, which is due to its independence on maternal factors ideally suited for such experimental manipulations. On of the recent outcomes of this project is a paper comparing the effects of drugs commonly used for heart rhythm control in pregnant women on developing cardiovascular system (Kočková et al., 2013).